Article Posted on : - Sep 30, 2011

NEOWISE has observed more than 100 thousand asteroids in the main belt between Mars and Jupiter from January 2010 and February 2011. Photo: NASA.

PASADENA (BNS): NASA's Wide-field Infrared Survey Explorer (WISE) has discovered more than 90 percent of the largest near-Earth asteroids which can pose a serious hazard for Earth, the space agency said Thursday.

Astronomers now estimate there are roughly 19,500 -- not 35,000 -- mid-size near-Earth asteroids.

The survey project, called NEOWISE has observed more than 100 thousand asteroids in the main belt between Mars and Jupiter, in addition to at least 585 near Earth from January 2010 and February 2011.

WISE captured a more accurate sample of the asteroid population than previous visible-light surveys because its infrared detectors could see both dark and light objects. It is difficult for visible-light telescopes to see the dim amounts of visible-light reflected by dark asteroids. Infrared-sensing telescopes detect an object's heat, which is dependent on size and not reflective properties.

In 2009, NASA launched WISE to map the whole sky to search for hidden asteroids, comets and other celestial objects.